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Abstract: Electronic structure of bismuth telluride nanowires with the growthdirections 110 and 015 is studied in the framework of anisotropic effectivemass method using the parabolic band approximation. The components of theelectron and hole effective mass tensor for six valleys are calculated for bothgrowth directions. For a square nanowire, in the temperature range from 77 K to500 K, the dependence of the Seebeck coefficient, the electron thermal andelectrical conductivity as well as the figure of merit ZT on the nanowirethickness and on the excess hole concentration are investigated in theconstant-relaxation-time approximation. The carrier confinement is shown toplay essential role for square nanowires with thickness less than 30 nm. Theconfinement decreases both the carrier concentration and the thermalconductivity but increases the maximum value of Seebeck coefficient in contrastto the excess holes impurities. The confinement effect is stronger for thedirection 015 than for the direction 110 due to the carrier mass differencefor these directions. The carrier confinement increases maximum value of ZT andshifts it towards high temperatures. For the p-type bismuth telluride nanowireswith growth direction 110, the maximum value of the figure of merit is equalto 1.3, 1.6, and 2.8, correspondingly, at temperatures 310 K, 390 K, 480 K andthe nanowire thicknesses 30 nm, 15 nm, and 7 nm. At the room temperature, thefigure of merit equals 1.2, 1.3, and 1.7, respectively.



Autor: I. Bejenari, V. Kantser

Fuente: https://arxiv.org/







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